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By Keizo Uematsu, Satoshi Tanaka, Nozomu Uchida, Yutaka Saito

"Effect of moisture content must be fully understood for controlling the granule compaction of ceramics. It changes the mechanical behavior of spray-dried granules applied for compaction process, and governs the structure and properties of .ceramics. To understand the time-dependent change in processing, the kinetics was examined for change of moisture content for granules placed in a die and the pressed compacts also. The results were explained in terms of apparent moisture diffusion coefficients. They varied non-linearly with the PVA content in the granules. The results were explained through the non-uniform PVA distribution in the granules.IntroductionMoisture must be controlled in compaction process to produce the green compacts having uniform structure. It affects glass transition temperature of binder and thus the deformation behavior of powder granules under an applied stress. Several studies [1-7] have clarified the effect of moisture content on the compaction behavior of granules and the structure of resultant compacts for both die pressing and cold isostatic pressing (CIP) of pre-formed compacts. In these studies, the moisture contents in the system were equilibrated with the humidity in the atmosphere before compaction. In practice, however, the moisture content in the system may vary with time if the relative humidity of surrounding atmosphere is different from what the granules were equilibrated previously. This is very likely case in real production processes. However, the kinetics of moisture change in the granules as well as in the pre-formed powder compacts have not been well studied. For controlling the microstructure in a system, it is necessary to fully understand the kinetics of moisture change and its relevance to packing structure of powders."

Jan 1, 2000

By John K. Wright

The segregation process involves heating oxide-type ores with a halide salt in the presence of a solid reductant. By a complex series of cyclic vapour-phase reactions, the desired metal is extracted from its original position in the ore and segregated to the vicinity of the reductant. In this form it is then amenable to concentration by physical methods. In this work the segregation behaviour or eight different nickel laterite ores has been examined using a laboratory rotary kiln. It was found that the silicate (serpentine) ores responded better to the segregation conditions used than did the limonitic ores. An examination of the segregated metal particles showed that they consisted of ferro-nickel. The concentration of nickel in the metallics was sensitive to the ore types and the segregation roasting conditions.

Jan 1, 1994

By O. P. Pandey, Rama Arora, Gurmel Singh, Suresh Kumar

The tribological behavior of Dual Particles Size (DPS) rutile reinforced LM13 alloy composite was investigated under varying applied pressure from 125 kPa to 625 kPa at a constant sliding speed of 1.6 m/s. In the present studies, 15 wt.% of rutile particles of different sizes (50-75 μm and 106-125 μm) are reinforced in the Al-12Si alloy (LM13) by liquid metallurgy route. Microhardness of the prepared samples was measured in different phases. Microstructure, wear mechanism and surface morphology of the wear surfaces and debris was observed under optical and scanning electron microscope. The change in wear behavior has been explained with reference to the observed EDS analysis of the wear track and debris. However, an interesting change in wear feature, mild to severe wear transition at critical pressure was noticed in wear behavior of the composite. The Al-DPS composite has immense potential to be used as a component material for tribological applications.

Jan 1, 2015

By Denise C. R. Espinosa

The amount of secondary batteries are increasing about 15% by year. Among these batteries, it can be highlighted the NiCd ones, due to their high consumption. In Brazil, the consumption of NiCd batteries grown quickly in the last 5 years, due to the dissemination of cellular telephones and other electronic devices. The first step of a process to recycle spent NiCd batteries is the pretreatment through unit operations of mining treatment. The aim of this work is to define a physical pretreatment to conditioning the waste to a pyrornetallurgical recycling process of spent NiCd batteries used in cellular telephones. Batteries were disassembled by hand to release the different components. The studied batteries are basically composed (by weight) of: 78% nucleus, 18% plastic case and 2% circuits. The grinding of the batteries was performed by knife mill and also by hammer mill. After grinding the material was screened and submitted to a magnetic separator.

Jan 1, 2001

By A. Filzwieser

The highest current density suitable for the electrowinning process is between 50 to 60 % of its limiting current density. One of the most important influences on the limiting current density is the thickness of the hydrodynamic boundary layer near the electrode surface. Therefore, the fluid flow in a copper electrowinning cell is calculated. The numerical simulation - using the CFD-software package FIRE® - considers all three different types of the fluid flow, namely, the natural convection, the forced convection by electrolyte circulation and the forced convection by electrochemically induced gas stirring. The simulation of natural convection is based on the different density values in the boundary layer at the electrode surface given by a density/concentration correlation. The copper concentration - linked with the current density by Faraday law - is solved by an additional transport equation. The simulation of the forced convection by the electrochemically-induced gas stirring is done by using a real two-phase calculation. That means that all differential equations are solved again for the second phase. The numerical solution of the fluid flow field is compared with the results of LDA- measurements, which were done in a special cell. The software for the LDA enabled a calculation of the void fraction possible and therefore a rough estimate of the mass transfer coefficient through the prevailing gas bubble induced convection can be made by assuming the influence of relative bubble volume.

Jan 1, 1999

By Sang-Joon Kim, Hae-Geon Lee, Hyun-Jin Cho

"Decarburization phenomena on the surface of liquid iron have been simulated by numerical method and the results were compared to the experimental data. During the DeC process in a converter, a large amount of splashed droplets are generated from the top surface of the bath and consequently the reaction surface area is increasing tremendously. Since the decarburization mainly occurs at the interface, it is important to understand the reactions on the liquid iron droplets. The flow and species concentration fields around liquid droplets taking into account the reaction of carbon with oxygen at the interface were calculated by a commercial CFD code FLUENT which solving multiphase Navier-Stokes equation with Volume Of Fluid method, species transport equations and energy transport equation. The initial carbon concentration was fixed to 4 wt% and the concentrations of oxygen in the atmosphere were varied from 5 to 50 wt%. As comparing the numerical calculation with experimental data written in the reference, the results have a good agreement for decarburization rate.IntroductionIn a primary steelmaking process, one of the main functions is to decarburize from hot metal and the 4% of carbon is decreased to about 0.5% of carbon. Even though there are some possible reactions leading to the removal of carbon from hot metal, the main reaction occurs on the free surface by direct oxidation of carbon at the gas-liquid interface with producing the carbon monoxide gas. In many metallurgical processes involving a jet impinging onto a steel bath surface, especially in a Basic Oxygen Furnace (BOF) converter, it is important to understand the behavior of molten iron droplets splashing out of the steel. The iron droplets are generated by an oxygen or air jet blowing and it increases the total surface area of liquid iron tremendously. Since the decarburization reaction is mainly affected by the surface area, it is necessary to verify the decarburization phenomena around the splashed droplets from liquid iron in order to allow an analysis ofBOF process possible."

Jan 1, 2011

By Jin-Chun Kim

Nanosized W based powders (W, WC, WC-Co) were produced by chemical vapor condensation (CVC) process. Two different solid W(CO)6 and Co2(CO)8 metal-organic materials were used as precursors. CVC experiment was conducted in the temperature range of 400-1100. As-CVC WC1-x powder which had non-stoichiometric composition was carburized by using of the CH4-H2 mixed gas in temperature range of 750-850. The CVC W and WC1-x powders showed loosely agglomeration structure, and the Co powder had intricate long stand structure because of intrinsic magnetic properties of Co phase. Carbon content of the CVC powders controlled by gas-phase carburization was well matched with theoretical WC stoichiometry (6.13wt%).

Jan 1, 2006

By S. W. White

Plasma arc technology is increasingly being used to process a number of waste materials. In present research, plasma technology is being investigated to treat waste magnesium baghouse dust, which is a waste material from the Magnetherm process. This dust contains mostly MgO, but also contains NazO, CaO, and KzO. Plasma energy is to be used along with a reducing agent to produce pure gaseous magnesium while keeping the other materials in a slag. The magnesium will then be collected by rapid quenching. A non-transferred arc plasma torch is ideal for this reaction because of its high enthalpy and improved energy efficiency over conventional methods. Another advantage of plasma is that it allows for the pre-heating or pre-reacting of fine particles before contact with the melt. Thermodynamic calculations using the Gibb energy minimization method were used to determine the most stable compositions of the materials at various temperatures. Energy balances have also been calculated. These results conclude that we can recover approximately 98% of the magnesium with a proper quenching technique. The calculated results are compared with the experimental data, and good agreement between them was observed.

Jan 1, 1999

By Ho-Sang Sohn

Copper concentrate particles of 200 to 300 mesh size were fed from the top of vertical reaction tube of 2.8 cm ID and 2 m long with an O2-N2 gas mixture. The reaction tube was heated to 900 K to 1100 K. The residence time of the particles in the reaction tube was about 1 second. The copper concentrate particles were very rapidly oxidized and melted down during their descent in the reaction tube. The particle temperature were calculated by combining an un-reacted core model, mass transfer between gas and particles, and heat transfer between gas, particles and tube wall. The particle temperature reached its maximum within a distance of 60 cm from the top of reaction tube, and it attained at 2000 K at higher oxygen partial pressure. The most particles were melted at the oxygen partial pressure above 20 kPa. An appreciable amount of As, Sb and Pb in the concentrate particles was eliminated in the upper portion of the reaction tube and the rate of elimination are explained by the rate of mass transfer of volatilized species through the gas film on the particle surface and the variation of particle temperature during the descent.

Jan 1, 2006

By Seiji Yokoyama

As a series of fundamental study on the gas evaporation method, a levitation-melted aluminum was evaporated in the gas mixture of argon and ammonia to synthesize ultrafine particles of aluminum nitride. When the ammonia partial pressure were more than 2kPa, the formation ratio of aluminum nitride was about 95%. The particles of aluminum nitride were mainly hexagonal. The mean size of the particles of aluminum nitride was about 57 nm, and it was constant without depending on the temperature of the levitated aluminum and the partial pressure pf ammonia. The aluminum nitride was formed by the reaction between ammonia and condensed liquid aluminum particle whose size was relatively small.

Jan 1, 2006

By Kimura. E.

Continuous estimation of phosphorus content of molten copper is required to produce phosphorus deoxidized copper in a continuous casting operation. The phosphorus content of molten copper was related to its electric resistivity, which was measured by the four-probed technique with a specially-shaped cell. In a laboratory scale, the linear relationship between the above factors was confirmed in the temperature range of 1083OC through 1200°C. The phosphorus concentration range measured was from 40 to 500 ppm. The phosphorus content was monitored successfully by measuring the electric resistivity of the molten copper in the distributor of a continuous caster in an industrial scale.

Jan 1, 1992

By Shantanu Chakrabarti, Khursid Alam Khan

"Globally, the use of metallic coated steel sheets in the automobile industry is increasing. The sheet should have excellent formability, weldability, paintability and corrosion resistance. Since bare cold rolled steel sheets have certain limitations, application of galvanized steel sheets is steadily expending. Galvannealed steel sheet fulfills all requirements and has become of major interest in the automobile industry.The success of Galvannealed (GA) steels in the body-in-white depends upon material design and parameters of various processes involved, like cold rolling, continuous annealing, hot dipping and galvannealing. In the present work, powdering resistance, one of the important product characteristics of GA, has been studied and a relation is established between the process parameters and the powdering value. The product obtained through optimization of the process parameters have been successfully used by major automotive producers without any powdering problem, for internal as well as external automotive applications.IntroductionThe present automotive industry demands that steel for the auto components should have excellent formability, weldability, paintability, corrosion resistance etc. In addition to this there is specific requirement for some particular components like high surface quality for skin panels. Corrosion resistance of panels is important requirment which determines the life of the particular component and brand value of the automotive. Among all the zinc based steel coating used in the automotive industry coating produced by Galvannealing process has received most attention because of its excellent weldability along with superior corrosion resistance and better paintability."

Jan 1, 2012

By H. Forrest

Lead smelting at Cookson Industrial Materials was formerly carried out using a combination of Blast and Reverberatory Furnaces. In the late 70' s these furnaces were replaced by two 20 tonne capacity Rotary Furnaces. This furnace type has proved to be more flexible in the range of feedstock that can be processed, including lead drosses, battery plate and even whole batteries. High rates of production have been achieved whilst attaining a good level of environmental control. The majority of the sulphur in the feedstock can be fixed by use of appropriate fluxes.

Jan 1, 1990

By Marcelo E. Andia

In Chile, a significant amount of mining takes place in varied geographical environments. Mining activity extends from copper and gold deposits located in the Atacama Desert 4.500 meters above sea level to underground coal workings beneath the sea floor. This diversity in location and environment presents many challenges in the development of competitive and environmentally sustainable mining activities. An important future issue will be how to close these mines in an appropriate way once economically exploitable ore reserves have been exhausted. This poses challenges for both the government and companies alike, considering that Chilean law currently lacks legislation specific to mine closure. This paper examines the risks associated with mine closure based on international experience, and identifies those risks specific to Chilean regions. The main regions in Chile where mine closure legislation should be applied are identified.

Jan 1, 1999

By Wei Yin, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

Copper anode slime is an increasingly significant resource for precious metals such as Au, Ag and Pd. The extraction of Au, Ag and Pd from decopperized anode slime by different pretreatments and different lixiviants including cyanide, chloride, thiourea and thiosulfate have been investigated. When oxidizing roasting pretreatment was carried out under the conditions of roasting time 120min and temperature 625 ℃, the removal ratios of S and Sb could reach 82.18% and 98.52%, respectively. And the following alkaline leaching of calcine could result in the dissolution of 46.40% Cu and 98.48% Pb. The optima leaching ratios of Au, Ag and Pd reached 99.48%, 97.69%, 94.79% by cyanide leaching, and 95.01%, 79.84%, 96.59% by chloride leaching, and about 95.21%, 95.66%, 48.79% by thiourea/thiosulfate leaching.

Jan 1, 2015

Acid generation from reactive sulphide mineral tailings has become a major environmental problem in the mining industry. Initiation of chemical and biochemical oxidation reactions of the sulphide mineral leads to acid generation. A novel concept of safe disposal and utilization of reactive fine mill tailings is presented in this paper. The paper also presents the results of a preliminary laboratory experimental .study of the concept. The tailings are agglomerated using portland cement as a binder. The cold bonded agglomerates are encapsulated with other chemical additives to act as acid neutralizers, oxygen and ironoxidizing bactericides., The primary. factors influencing the choice of bacterfoides to inhibit the acid generating bacteria are their costs, toxicity and environmental friendliness. The paper discusses the utilization of agglomerated' products as aggregates for underground backfill, or as gravel for surface land cover.

Jan 1, 1991

By Wentao Guo, Xuefeng She, Qingguo Xue, Jingsong Wang

By the coke gasified reaction device and online measurement high-temperature compressive strength apparatus, the variation of pore structures of coke after gasified reaction with CO2 and H2O was investigated. Research illuminating the influences of solution loss rate, temperature, and carbon species on compressive strength of coke was also carried out. The results showed that the total compressive strength was higher than for the reaction with CO2. The high-temperature compressive strength of coke decreased with the increasing of solution loss ratio or temperature after reacting with CO2 and H2O. At the same solution loss ratio, the damage of pore structure to coke strength after gasified reaction with H2O was relatively smaller and the deformation resistance was stronger when compared with that in CO2.

Jan 1, 2016

By Wolfgang Steffes-Tun

Pyrite ore concentrate from the Meggen mine (FRG) , which contains about 0 300 400 ppm thallium, is roasted in a fluid bed furnace at 1000 -1100 C to form sulfur dioxide and ash consisting mainly of hematite. Subsequently, the sulfur dioxide is separated from the ash or dust during several steps while cooling to about 250oC. The pyrite ash fractions show decreasing grain size down to 5 pm, a pH-decrease down to 2,4 and a marked enrichment of arsenic and thallium by a factor of 12. In the final fraction, the hot electroprecipitator dust of the dump (EGR), minute crystals of thallium-containing jarosite can be detected by analytical transmission electorn microscopy (TEM). Under oxidizing, acid conditions, jarosite may be a possible "reservoir mineral" for immobilizing thallium.

Jan 1, 1989

By T. V. Jayaraman

Fe-Ga alloys, with compositions around 27.5 at % Ga, can be heat treated to obtain ? (ordered bcc), DO19 (ordered hexagonal), and L12 (ordered fcc) ordered structures. Our earlier work using polycrystalline samples had shown that magnetostriction is strongly influenced by ordering in this alloy. Here more detailed study of the correlation between ordering and magnetostriction using single crystals of Fe 27.5 at. % Ga alloys is reported. Single crystals of Fe 27.5 at % Ga were grown using Bridgman single crystal growth technique. X-ray and electron diffraction were used to study the ordering in this alloy. Magnetostriction measurements were carried out at no load conditions. Elastic constants were measured using Resonant Ultrasound Spectroscopy.

Jan 1, 2006

By Michael S. Moats, Daniel Kim, Shijie Wang

"The behavior and deportment of lead, arsenic, antimony and bismuth are critical in producing high quality cathode by copper electrorefining. A critical review of research related to these elements is presented along with a comparison to industrial data, where appropriate. These elements exist predominantly in the anode as complex oxides along die grain boundaries. Upon dissolution, Group 15 elements report both to the electrolyte and slimes while lead essentially enters the slimes. The deportment of the Group 15 elements appears to be influenced by several chemical interactions which are discussed. The effect of these elements on floating slimes and anode passivation is reviewed. Under normal electrorefining conditions, lead, antimony and bismuth are thought to enter the cathode through the encapsulation of slime particles. The literature indicates that arsenic enters the cathode predominately by electrolyte entrainment. Finally, areas for future research regarding these elements are presented.IntroductionControlling lead, arsenic, antimony and bismuth is critically important for the production of high quality cathode in copper electrorefining. The reasons for this are twofold. First, ASTM Grade 1 Cathode specifications [1] for these elements are low, as listed in Table 1. Second, they can affect the efficiency of the electrorefining process (e.g., through passivation, current efficiency, slime processing)."

Jan 1, 2012